1. Technical Field of the Invention
This invention relates to a method for the catalytic reductive amination of a poly(oxytetramethylene) glycol in order to provide the corresponding poly(oxytetramethylene) diamine in high yield and with good selectivity.
More particularly, this invention relates to an improvement in the method for the catalytic reductive amination of a poly(oxytetramethylene) glycol in the presence of hydrogen and ammonia under reductive amination conditions wherein the reaction is conducted in the presence of a catalyst composed of nickel, copper, chromium and molybdenum and containing, on an oxide-free basis, about 70 to about 75 wt. % of nickel, about 20 to about 25 wt. % of copper, about 0.5 to 5 wt. % of chromium and about 1 to 5 wt. % of molybdenum.
Still more particularly, this invention relates to a process wherein a poly(oxytetramethylene) glycol, excess ammonia and hydrogen are passed through a bed of a pelleted nickel, copper, chromium, molybdenum catalyst on a continuous basis in order to continuously provide a reaction product comprising the poly(oxytetramethylene) diamine corresponding to the poly(oxytetramethylene) glycol feedstock.
2. Prior Art
Methods for the preparation and use of poly(oxytetramethyl) qlycols are disclosed in Smith et al. U.S. Pat. Nos. 3,824,198, 3,824,219, and 3,824,220, patented July 16, 1974. Other patents disclosing methods for making and using poly(oxytetramethyl) glycols and poly(oxytetramethyl) diamines include Hubin et al. U.S. Pat. No. 3,436,359 patented Apr. 1, 1969 and Leir et al. U.S. Pat. No. 4,833,213, patented May 23, 1989.
The catalyst to be used in conducting the process of the present invention is suitably a catalyst of the type disclosed in Moss et al. U.S. Pat. No. 3,151,115 wherein reductive amination catalysts are disclosed containing nickel, cobalt and copper or mixtures thereof and chromium oxide, molybdenum oxide, manganese oxide, thorium oxide and mixtures thereof.
The preferred catalyst disclosed by Moss et al. is a nickel, copper, chromia catalyst containing, on an oxide-free basis, from about 70 to 75 wt. % of nickel, about 20 to about 25 wt. % of copper and about 1 to about 5 wt. % of chromium.
Renken et al. U.S. Pat. No. 4,618,717, issued Oct. 21, 1986 is directed to a method for reductively aminating ethylene glycol monoalkyl ethers in order to provide the corresponding primary amines using a catalyst composed of about 50 to 90 wt. % of nickel, about 10 to 50 wt. % of copper and about 0.5 to 5 wt. % of an oxide of chromium, iron, titanium, thorium, zirconium, manganese, magnesium or zinc. Larkin et al. U.S. Pat. No. 4,766,245, issued Aug. 23, 1988 discloses a method for reductively aminating polyoxyalkylene diols and triols in the presence of a Raney nickel/aluminum catalyst.
The purification of tertiary butyl alcohol by the catalytic decomposition of impurities such as tertiary butyl hydroperoxide is disclosed in a series of patents. The catalyst of Marquis et al. U.S. Pat. No. 4,758,681, issued July 19, 1988, contains about 30 to 60 wt. % of nickel, about 5 to 40 wt. % of copper, about 1 to 30 wt. % of iron and about 0.5 to 10 wt. % of chromium. Sanderson et al. disclose the use of a catalyst containing 20 to 80 wt. % of iron, 5 to 40 wt. % of copper, 0.1 to 10 wt. % of chromium and 0.01 to 5 wt. % of cobalt for this purpose. In Sanderson et al. U.S. Pat. No. 4,742,179, the catalyst that is used for this purpose contains 1 to 20 wt. % of iron and 1 to 6 wt. % of chromium, the balance being composed of a mixture of nickel and copper, while the catalyst of Sanderson et al. U.S. Pat. No. 4,873,380, issued Oct. 10, 1989 is composed of 1 to 20 wt. % of barium, 1 to 6 wt. % of chromium and the balance a mixture of nickel and copper.